1. Field of the Invention
The present invention relates generally to the placement of fractures in wellbores and, more particularly, to a method of placing multiple stage fractures in an uncemented lined horizontal wellbore.
2. Description of the Related Art
Operators are increasingly completing horizontal wells in tight reservoirs where fracturing is required to achieve economic hydrocarbon production. Traditionally, these wells are completed with multiple fractures which are individually isolated along the wellbore during the fracturing process, by either cementing the liner in place or using external casing packers or other mechanical isolation methods.
There are a number of drawbacks to the conventional methods. First, cementing the annulus severely limits the production efficiency of the well because the cement prevents any matrix production into the wellbore from the unstimulated interval between the fractures. Second, the use of mechanical packers and the associated ball operated frac sleeves that provide communication through the liner adds significant cost to the wells.
Techniques to perform multiple fractures in the openhole have been developed to combat some of these problems. One commercially available method exploits the use of jetting tools, conveyed on coiled tubing, together with annular fracturing techniques. However, these fracturing techniques cannot eliminate fracture fluid leaking off to the induced fractures lower in the well and, oftentimes, it is unpredictable as to where the fluid is going and, thus, how the fracture is propagating. Moreover, this and other open hole techniques are accompanied by certain practical difficulties, such as differential sticking and packing of the proppant around the jetting tool. Also, using a liner alone without any annular flow containment mechanisms risks fluid traveling along the annulus and propagating along previous fractures.
In view of these drawbacks, there is a need in the art for an improved, less expensive method of completing wells, whereby placement of discrete fractures along the wellbore is allowed, while maintaining fluid communication along the annulus between the formation and any installed liner.